Users will see sleep stage data on Apple watch in the app and can view more detailed information, like time asleep, alongside additional metrics, like heart rate and respiratory rate, in sleep comparison charts in the health app on iPhone.
Using signals from the accelerometer and heart rate sensor, an Apple watch can now estimate when users are in REM, core, or deep sleep, and when they are awake. Sleep tracking in watchOS 9 includes sleep staging. On Monday, Apple released watchOS 9, the latest version of the watchOS operating system designed to run on newer Apple watch models.
